A wide variety of soil release agents for use in domestic and industrial fabric treatment processes such as laundering, fabric drying in hot air clothes dryers, and the like are known in the art. Various soil release agents have been commercialized and are currently used in detergent compositions and fabric softener/antistatic articles and compositions. Such soil release polymers typically comprise an oligomeric or polymeric ester "backbone".
Soil release polymers are generally very effective on polyester or other synthetic fabrics where the grease, oil or similar hydrophobic stains spread out and form a attached film and thereby are not easily removed in an aqueous laundering process. Many soil release polymers have a less dramatic effect on "blended" fabrics, that is on fabrics that comprise a mixture of cotton and synthetic material, and have little or no effect on cotton articles. The reason for the affinity of many soil release agents for synthetic fabric is that the backbone of a polyester soil release polymer typically comprises a mixture of terephthalate residues and ethyleneoxy or propyleneoxy polymeric units; the same or closely analogous to materials that comprise the polyester fibers of synthetic fabric. This similar structure of soil release agents and synthetic fabric produce an intrinsic affinity between these compounds.
Extensive research in this area has yielded significant improvements in the effectiveness of polyester soil release agents yielding materials with enhanced product performance and formulatability. Modifications of the polymer backbone as well as the selection of proper end-capping groups has produced a wide variety of polyester soil release polymers. For example, end-cap modifications, such as the use of sulfoaryl moieties and especially the low cost isethionate-derived end-capping units, have increased the range of solubility and adjunct ingredient compatibility of these polymers without sacrifice of soil release effectiveness. Many polyester soil release polymers can now be formulated into both liquid as well as solid (i.e., granular) detergents.
In contrast to the case of polyester soil release agents, producing an oligomeric or polymeric material that mimics the structure of cotton has not resulted in a cotton soil release polymer. Although cotton and polyester fabric are both comprised of long chain polymeric materials, they are chemically very different. Cotton is comprised of cellulose fibers that consist of anhydroglucose units joined by 1-4 linkages. These glycosidic linkages characterize the cotton cellulose as a polysaccharide whereas polyester soil release polymers are generally a combination of terephthalate and oxyethylene/oxypropylene residues. These differences in composition account for the difference in the fabric properties of cotton versus polyester fabric. Cotton is hydrophilic relative to polyester. Polyester is hydrophobic and attracts oily or greasy dirt and can easily be "dry cleaned". Importantly, the terephthalate and ethyleneoxy/propyleneoxy backbone of polyester fabric does not contain reactive sites, such as the hydroxyl moieties of cotton, that interact with stains in different manner than synthetics. Many cotton stains become "fixed" and can only be resolved by bleaching the fabric.
Until now the development of an effective cotton soil release agent for use in a laundry detergent has been elusive. Attempts by others to apply the paradigm of matching the structure of a soil release polymer with the structure of the fabric, a method successful in the polyester soil release polymer field, has nevertheless yielded marginal results when applied to cotton fabric soil release agents. The use of methylcellulose, a cotton polysaceharide with modified oligomeric units, proved to be more effective on polyesters than on cotton.
For example, U.K. 1,314,897, published Apr. 26, 1973 teaches a hydroxypropyl methyl cellulose material for the prevention of wet-soil redeposition and improving stain release on laundered fabric. While this material appears to be somewhat effective on polyester and blended fabrics, the disclosure indicates these materials to be unsatisfactory at producing the desired results on cotton fabric.
Other attempts to produce a soil release agent for cotton fabric have usually taken the form of permanently modifying the chemical structure of the cotton fibers themselves by reacting a substrate with the polysaccharide polymer backbone. For example, U.S. Pat. No. 3,897,026 issued to Kearney, discloses cellulosic textile materials having improved soil release and stain resistance properties obtained by reaction of an ethylene-maleic anhydride co-polymer with the hydroxyl moieties of the cotton polymers. One perceived drawback of this method is the desirable hydrophilic properties of the cotton fabric are substantially modified by this process.
Non-permanent soil release treatments or finishes have also been previously attempted. U.S. Pat. No. 3,912,681 issued to Dickson teaches a composition for applying a non-permanent soil release finish comprising a polycarboxylate polymer to a cotton fabric. However, this material must be applied at a pH less than 3, a process not suitable for consumer use nor compatible with laundry detergents which typically have a pH greater than 7.5.
U.S. Pat. No. 3,948,838 issued to Hinton, et alia describes high molecular weight (500,000 to 1,500,000) polyacrylic polymers for soil release. These materials are used preferably with other fabric treatments, for example, durable press textile reactants such as formaldehyde. This process is also not readily applicable for use by consumers in a typical washing machine.
U.S. Pat. No. 4,559,056 issued to Leigh, et alia discloses a process for treating cotton or synthetic fabrics with a composition comprising an organopolysiloxane elastomer, an organosiloxaneoxyalkylene copolymer crosslinking agent and a siloxane curing catalyst. Organosilicone oligomers are well known by those skilled in the art as suds supressors
Other soil release agents not comprising terephthalate and mixtures of polyoxy ethylene/propylene are vinyl caprolactam resins as disclosed by Rupert, et alia in U.S. Pat. Nos. 4,579,681 and 4,614,519. These disclosed vinyl caprolactam materials have their effectiveness limited to polyester fabrics, blends of cotton and polyester, and cotton fabrics rendered hydrophobic by finishing agents.
Examples of alkoxylated polyamines and quaternized alkoxylated polyamines are disclosed in European Patent Application 206,513 as being suitable for use as soil dispersents, however their possible use as a cotton soil release agent is not disclosed. In addition, these materials do not comprise N-oxides, a key modification made to the polyamines of the present invention and a component of the increased bleach stability exhibited by the presently disclosed compounds.
It has now been surprisingly discovered that laundry detergent compositions which comprise non-homogeneous backbone polyamines when used in combination with surfactants and a hydrophobic soil dispersant provides enhanced soil release from cotton fabric. The compositions of the present invention are surprisingly well suited form use in hand washing of fabric.